Liquid Crystal Display Light Guide Plate Tilted Reflector
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Solution Overview
Problem
Conventional liquid crystal display devices with backlight units using light guide plates face challenges in improving light reuse efficiency without increasing device size, as the most intense light component from LEDs is not effectively reused due to improper arrangement of reflectors and reflective polarizing plates, leading to reduced brightness and battery life in portable devices.
Innovation Solution
A liquid crystal display device design that includes a reflective polarizing plate and a reflector tilted at an angle to convert S-polarized light to P-polarized light, with a polarization converter like a ¼ wavelength plate, ensuring efficient light reuse by directing the converted light parallel to the main light component's travel direction, thereby enhancing light transmission efficiency without increasing the device's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective polarizing plate is used to reduce light absorption by the polarizing plate, then light use efficiency is improved, but the light use efficiency is increased only up to 1.3 times instead of the expected 2 times
Solution Approach 1:
A 1/4 wavelength plate is introduced as an intermediary component between the light source and the reflective polarizing plate. This wavelength plate converts the polarization state of light, enabling the reflective polarizing plate to reflect S-polarized light effectively while allowing P-polarized light to pass through, thereby achieving the expected 2x light use efficiency improvement
Solution Approach 2:
The invention changes the polarization state parameter of light by using a 1/4 wavelength plate to convert linearly polarized light into circularly polarized light or vice versa. This parameter change enables the reflective polarizing plate to function as intended, separating P and S polarized components effectively and achieving optimal light reuse
2Device complexity
If the reflective polarizing plate and reflector are disposed in parallel to the light guide plate to simplify structure, then device complexity is reduced, but the most intense light component is not effectively reused
Solution Approach 1:
The invention tilts the reflective polarizing plate and reflector at a specific angle (e.g., 45 degrees) relative to the light guide plate, transitioning from a parallel arrangement to an angular arrangement. This dimensional change in orientation enables the most intense light component to be reflected and reused effectively while maintaining structural simplicity
Solution Approach 2:
The reflective polarizing plate and reflector are disposed asymmetrically at a tilted angle rather than in parallel symmetry. This asymmetric arrangement optimizes the optical path for light reuse, ensuring that the most intense light component from the LED is effectively redirected and reused without increasing device complexity
3Illumination intensity
If the number of pixels is increased from QVGA to VGA to improve image quality, then image quality is improved, but the aperture ratio decreases making it difficult to improve brightness and battery life
Solution Approach 1:
The invention recovers and reuses light that would otherwise be lost or absorbed by the polarizing plate. By using a reflective polarizing plate combined with a 1/4 wavelength plate, the system recovers S-polarized light and redirects it through the liquid crystal layer, effectively doubling the light use efficiency. This recovered light compensates for the reduced aperture ratio in high-resolution displays
Solution Approach 2:
The invention ensures continuous useful action by recycling light multiple times through the liquid crystal layer. The reflective polarizing plate and reflector create an optical path that allows light to pass through the liquid crystal layer, be reflected, and pass through again, maximizing the utilization of each photon and improving overall display efficiency without requiring higher aperture ratios
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves light use efficiency, allowing for higher brightness with the same power consumption or reduced power consumption with the same brightness, enhancing visibility in bright environments and extending battery life in portable devices.
Implementation Method 1
a polarization converting member for converting the S-polarized component of light to a P-polarized component
Implementation Method 2
a reflective polarizing plate for transmitting a P-polarized component and reflecting an S-polarized component of the light emitted from the plurality of light sources
Implementation Method 3
a reflector for reflecting the S-polarized component of light reflected by the reflective polarizing plate
Data Source
AI summary
Provided is a liquid crystal display device with a backlight including a light guide plate. The light guide plate includes, a reflective polarizing plate for transmitting a P-polarized component and reflecting an S-polarized component, a reflector for reflecting the S-polarized component reflected by the reflective polarizing plate, and a polarization converting member for converting the S-polarized component to a P-polarized component. The reflective polarizing plate and the reflector are tilted at an angle such that reflecting surfaces thereof are not perpendicular to four sides of the liquid crystal display panel and are disposed such that the S-polarized component contained in a main component of light emitted from the light sources is reflected by the reflector. This keeps small the size of the liquid crystal display device and still improves reuse efficiency of the light emitted from the light sources.